The Irish standard. [volume] (Minneapolis, Minn. ;) 1886-1920, 1887-05-28

CELESTIAL PHoToGHAPHY.
Achle ve,nents Made Possible by the Re-
| cent Progress of the Art.
Although celestial photography is
! upward Of half century old, the moon
having been photographed by DR.. j.
w. Draper in 1910, yet within the past
two or three years it has become al
most new art. It's progress has been
so rapid that it has the effect of a fresh
| discovery. There is now no longer any
doubt that the hopes of astronomers in
| this direction can be realized, and that
the Photographic camera can be made
to take the place, and in some respects
more than take the. place, of the eye in
telescope work. Excellent photo
graphs are now obtained not only OF
the sun, the moon, the brighter stars,
comets and nebule, but also of the
spectra of many heavenly bodies, and
of phenomena, such as faint stars and
!! invisible nebul@, which the eye can not
detect at all, even when aided by the
most powerful telescope. A notable
discovery of this kind has been made
in the familiar group of stars called the
Pleiades. Apparently connected with
one Of these stars, which has been
known for ages under the name of
Maia, is a strange nebulous mass,
which is clearly seen in photographs
OF the Pleiades, taken in the past two
years, though no telescope shows any
trace Of it to the eye. Photographs Of
the heavens also show stars whose ex-
istence would have been unknown to
us but for tile marvellous power of the
Photographic plate to catch and hold
the image of objects too obscure to
sensibly affect the human retina.
There are two ways in which the
camera has an advantage over the eye.
First, it can accumulate impressions
that is to say, it is able by continued
exposure to obtain an image of an Oh
ject which may be so faint that a
shorter exposure would give no image.
This, Of course, is a power that the eye
does not possess. 1t is equivalent to
being able to see plainly by long gar
ing what can not be seen at all by a
brief inspection. Then the photo
graphic plate is sensitive to the So
called actinic rays, which do not pro-
duce the impression Of light, and con-
sequently do not affect the eye. Thus
photography furnishes astronomy with
All improved eye, capable of ranging
nobody yet knows how far into the
abysses OF the universe.
The recent progress of celestial
photography has been so great that it
has created Il new branch of observ;a-
tional astronomy, and, as in the use OF
the spectroscope, it has been found that
specialists are needed to fully develop
it. Achievements in the way of
measuring, sounding and mapping the
visible universe, which astronomers a
generation ago would hardly have
dared to dream of, are now clearly
within the range Of possible accom-
plslmcnt. 1t is regarded as en-
tile]y practicable to obtain within
the short space Of ten years
~ oSiloo VI piloeoSI sAPAAo A1ieAoeAAiAS cAAC
whole heavens, and containing millions
upon millions of stars that can not be
seen with the naked eye. The value of
such photographs to future astron-
omers would be inestimablc. Showing
the true places of so many stars at the
date when the photographs were made,
they would render 1t easy to detect any
changes Of place among the stars
Such changes are known to occur from
various causes in all quarters of the
heavens, but the difficulty has been to
measure them. BY the photographic
method, SCAR motions can be studied
with high degree Of accuracy; and
through such study astronomers can
arrive at d far more complete knowl-
edge than they now possess Of the form
and structure of the universe Of suns,
in which our own sun shines only as a
lunlinary Of minor rank.--N. Z.
Sun.